Bars in Local Galaxies: Evidence for a higher Optical Bar Fraction in Disk-Dominated Galaxies

TL;DR

This study analyzes the prevalence of large-scale bars in local disk galaxies, revealing a higher optical bar fraction in disk-dominated galaxies and suggesting minimal evolution of bar fractions from redshift 1 to 0.

Contribution

It provides a large-scale, quantitative analysis of bar fractions in local galaxies, highlighting the dependence on galaxy morphology and properties, and compares with higher redshift data.

Findings

Optical bar fraction in local galaxies is approximately 48-52%.

Bar fraction increases with galaxy disk dominance, color, and surface brightness.

Strong bars are present in about 34% of bright disk galaxies, with little change over redshift.

Abstract

We present a study of large-scale bars in the local Universe, based on a large sample of ~3692 galaxies, with -18.5 <= M_g < -22.0 mag and redshift 0.01 <= z < 0.03, drawn from the SDSS. Our sample includes many galaxies that are disk-dominated and of late Hubble types. Both color cuts and Sersic cuts yield a similar sample of ~2000 disk galaxies. We characterize bars and disks by ellipse-fitting r-band images and applying quantitative criteria. After excluding highly inclined (>60 degrees) systems, we find the following results. (1) The optical r-band fraction (f_opt-r) of barred galaxies is ~48%-52%. (2) When galaxies are separated according to normalized half light radius (r_e/R_24), a remarkable result is seen: f_opt-r rises sharply, from ~40% in galaxies that have small r_e/R_24 and visually appear to host prominent bulges, to ~70% for galaxies that have large r_e/R_24 and appear disk-dominated. (3) f_opt-r rises for galaxies with bluer colors and higher central surface brightness. A weaker rise is seen toward lower masses. (4) We find that ~20% of our sample of disk galaxies appear to be ``quasi-bulgeless''. (5) If we restrict our sample to bright galaxies and only consider bars that are strong (ellipticity >=0.4) and large enough (semi-major axis >=1.5 kpc) to be reliably characterized via ellipse-fitting out to z~0.8, we get an optical r-band fraction for strong bars f_opt-s of ~34%. This value is higher only by a modest factor of 1.4, compared to the value of ~24%+-4% reported at z~0.7-1.0. If one assumes that the increasing obscuration by dust and star formation over z~0 to 1.0 causes a further artificial loss of bars, the data even allow for a constant or rising fraction of strong bars with redshift.